Clinical characteristics of the included patients
| Non-BAL group | BAL group | n | p-value | |
| Subjects n | 96 | 107 | ||
| Male | 63 (66) | 61 (57) | 124 | 0.21 |
| Prematurity <35 WG | 16 (17) | 18 (17) | 34 | 0.98 |
| Age years (mean±sd) | 2.24±2.12 | 5.53±4.13 | 203 | <0.001 |
| <3 years | 72 (75) | 42 (39) | 114 | <0.001 |
| 3–6 years | 18 (19) | 26 (24) | 44 | 0.34 |
| >6 years | 6 (6.2) | 39 (36) | 45 | <0.001 |
| Age at onset months (mean±sd) | 6.15±8.98 | 12.5±21.6 | 200 | <0.01 |
| Atopy | ||||
| Patient# | 34 (47) | 83 (84) | 117 | <0.001 |
| Family# | 70 (80) | 90 (87) | 160 | 0.14 |
| Passive smoking# | 29 (35) | 37 (35) | 66 | 0.99 |
| Hospitalisation# | 79 (84) | 72 (68) | 151 | <0.01 |
| Hospitalisation (mean±sd) | 2.42±1.41 | 2.86±1.87 | 151 | 0.11 |
| ICU hospitalisation# | 22 (24) | 16 (15) | 38 | 0.12 |
| Current asthma symptoms | 29 (30) | 4 (3.7) | 33 | <0.001 |
| High-dose inhaled corticosteroids associated with another controller therapy# | 24 (25) | 70 (68) | 94 | <0.001 |
| Uncontrolled or partially controlled asthma | 72 (75) | 85 (79) | 157 | 0.45 |
| Systematised alveolar opacities on chest radiography# | 7 (8.1) | 5 (5.4) | 12 | 0.46 |
| Elevated eosinophils >500 per mm3# | 9 (13) | 19 (19) | 28 | 0.27 |
| Lung function tests | 3 (3.1) | 36 (33.6) | 39 | <0.001 |
| Normal | 3 (100) | 26 (72) | 29 | 0.56 |
Data are presented as n (%) unless otherwise stated. High-dose inhaled corticosteroids: according to GINA, inhaled fluticasone >200 µg·day−1 for children under 6 years old and >500 µg·day−1 over 6 years of age, inhaled budesonide >400 µg·day−1 under 12 years old and >800 µg·day−1 over 12 years old; nebulised budesonide >1000 µg·day−1 for all children. BAL: bronchoalveolar lavage; WG: weeks of gestation; ICU: intensive care unit. #: based on 171 to 200 patients. Significant p-values appear in bold.